Error Handling

ZZ has no exceptions. Fallible operations return Option or Result variants, and the compiler helps you handle every case.

Option: a value or nothing

Parsing, lookups and decodes return Option:

count := input("How many users? ") |> int() ?? 1

?? unwraps .some(v) to v and substitutes the fallback for .none. Match when you need to branch instead:

match env.get_var("HOME") {
    .some(home) => println("Home: {home}"),
    .none => println("HOME not set"),
}

Result: success or context

Filesystem, network and JSON operations return Result:

import std.fs

match fs.read_file("data.txt") {
    .ok(content) => println(content),
    .err(e) => println("Error: {e}"),
}

Unwrap with intent

Three methods document how much you care:

x := .some(42)
x.unwrap()           // 42 — panics on .none, use when impossible
x.unwrap_or(0)       // 42 — the common default
x.expect("missing")  // 42 — panics with YOUR message

y: Option<int> = .none
y.unwrap_or(0)       // 0

Prefer unwrap_or and ?? in normal code; reserve unwrap for invariants and expect for messages a future debugger will thank you for.

Exhaustive match

The compiler wants every case covered — _ is your catch-all:

match status {
    .ok(data) => render(data),
    .err(e) => log(e),
}

An uncovered value is a compile error, not a runtime surprise.

Diagnostics that teach

Typos get Levenshtein suggestions instead of a shrug:

error: undefined variable `printn`
  = did you mean `println`?

error: struct `Point` has no field `xz`
  = did you mean field `x`?

Warnings catch dead weight — unused imports and variables:

warning: unused import `pkg`
warning: unused variable `unused_var`

Every error carries a code, a span and a fix hint:

error[E001]: type mismatch
  --> src/main.zz:5:12
   |
 5 |     x: int = "hello"
   |     ----   ^^^^^^^^ expected int, found str
   |
   = help: cast string to int with `int()` function

Fix at machine speed

zz check src/     # report everything
zz fix src/       # apply safe auto-fixes
zz fix --hard     # apply ambiguous fixes too, no prompts

A typical auto-fix renames to suppress a warning:

warning[W001]: unused variable
  --> src/main.zz:3:5
   |
 3 |     x := 42
   |     ^^^^^^^
   |
   = help: prefix with `_` to suppress: `_x := 42`
   = fix: `_x := 42`